Among the alternative drive concepts for motor vehicles, fuel cell-supported systems, in particular, are currently generating a great deal of attention. These systems typically include PEM (polymer electrolyte membrane) fuel cells that operate with hydrogen and air as the energy carriers.
Because hydrogen refueling and storage in the motor vehicle remains a problem, hydrogen is produced directly on-board as needed in an upstream reformer stage from easy-to-handle fuels such as methanol, methane, diesel oil or gasoline and consumed immediately. The reformers employed for this purpose are chemical reactors that are used to partially oxidize the fuels by adding air and moisture, for example at a temperature of 800° C., in catalytic converters, producing hydrogen and other secondary products, such as CO and CO2.
Supplying the reformer with the educts needed for the reaction is thus a very important step. All educts, such as air, water and fuel, are typically supplied to the reformer in a gaseous state. This requires an evaporation tube that is able to provide the proper amounts of gaseous fuel and steam.
However, problems arise during the cold start phase, since the liquid educts cannot be vaporized by the reformer waste heat, but only by an electrically heated evaporator. In addition, conventional evaporators are unable to instantaneously generate the proper quantities of gaseous reactants when load change requirements vary abruptly.
Alternative concepts have thus been developed to inject fuels and water directly into the reformer in liquid form. However, to carry out the reaction in the reformer as efficiently as possible, the liquid educts must be introduced into the reformer in a finely dispersed form. A reactor for producing hydrogen that has a nozzle for injecting liquid hydrocarbons into an air stream is known from U.S. Pat. No. 3,971,847. The resulting mist is swirled on baffle plates before entering the actual reaction zone. However, the water needed for the reaction is evaporated separately in an evaporation tube.
The object of the present invention is to provide an atomizing nozzle for the simultaneous atomization of water and liquid fuels, with the atomizing nozzle having a very high degree of educt atomization and mixing and, in addition, being designed for instantaneous metering of liquid educts.